Large Output Signal Research Articles

Triboelectric Nanogenerators with Machine Learning for Internet of Things

AbstractThe development of the Internet of Things (IoT) indicates that humankind has entered a new intelligent era of the “Internet of Everything”. Thanks to the characteristics of low‐cost, diverse structure, and high energy conversion efficiency, the self‐powered sensing systems, which are based on the Triboelectric Nanogenerator (TENG), demonstrate great potential in the field of IoT. In order to solve the challenges of TENG in sensing signal processing, such as signal noise and nonlinear relations, Machine Learning (ML), which is an efficient and mature data processing tool, is widely applied for efficiently processing the large and complex output signal data generated by TENG intelligent sensing system. This review summarizes and analyzes the adaptation of different algorithms in TENG and their advantages and disadvantages at the beginning, which provides a reference for the selection of algorithms for TENG. More importantly, the application of TENG is introduced in multiple scenarios, including health monitoring, fault detection, and human‐computer interaction. Finally, the limitations and development trend of the integration of TENG and ML are proposed by classification to promote the future development of the intelligent IoT era.

Photon Induced Scintillation Amplifier — The PISA concept

Photoelectron signal amplification in gas photomultipliers (GPMs) is achieved through charge avalanche development in the holes of a cascade of hole-type microperforated foils. When a voltage difference is applied between the metal film electrodes that are deposited on both surfaces of those foils, an electric field with a high intensity is established inside the holes. As a consequence, each electron entering those holes produces an electron avalanche that emerges from the other side of the holes. A cascade of few foils is necessary for a single primary electron to produce a final avalanche intense enough to be read out, in the anode electrode, above the electronic noise. We propose the Photon Induced Scintillation Amplifier (PISA), where the photoelectron signal amplification is obtained by reading out the photon scintillation produced in the charge avalanches of solely one Micro-Hole-and-Strip-Plate-type microstructure with SiPMs. The optical readout has the advantage of having the extra gain from the photosensor and is less sensitive to electronic noise. A large photosensor gain produces large output signals that can travel over long distances without significant degradation. This allows for the readout electronics to be placed away from the photosensor and, thus, from the detector sensitive volume. The scintillation readout plane can be made of a 2D-array of SiPMs, with size and pitch in accordance with the needed scintillation level and position resolution. A first basic prototype was assembled to present a proof-of-principle of the PISA concept.

Perspective on nanoscale magnetic sensors using giant anomalous Hall effect in topological magnetic materials for read head application in magnetic recording

Recent advances in the study of materials with topological electronic band structures have revealed magnetic materials exhibiting giant anomalous Hall effects (AHEs). The giant AHE has not only attracted the research interest in its mechanism but also opened up the possibility of practical application in magnetic sensors. In this article, we describe simulation-based investigations of AHE magnetic sensors for applications to read head sensors (readers) of hard disk drives. With the shrinking of magnetic recording patterns, the reader technology, which currently uses multilayer-based tunnel magnetoresistance (TMR) devices, is associated with fundamental challenges, such as insufficient spatial resolution and signal-to-noise ratio (SNR) in sensors with dimensions below 20 nm. The structure of an AHE-based device composed of a single ferromagnetic material is advantageous for magnetic sensors with nanoscale dimensions. We found that AHE readers using topological ferromagnets with giant AHE, such as Co2MnGa, can achieve a higher SNR than current TMR readers. The higher SNR originates from the large output signal of the giant AHE as well as from the reduced thermal magnetic noise, which is the dominant noise in TMR readers. We highlight a major challenge in the development of AHE readers: the reduction in the output signal due to the shunting of the bias current and the leakage of the Hall voltage through the soft magnetic shields surrounding the AHE reader. We propose reader structures that overcome this challenge. Finally, we discuss the scope for future research to realize AHE readers.

Ferroelectric artificial synapses for high-performance neuromorphic computing: Status, prospects, and challenges

Neuromorphic computing provides alternative hardware architectures with high computational efficiencies and low energy consumption by simulating the working principles of the brain with artificial neurons and synapses as building blocks. This process helps overcome the insurmountable speed barrier and high power consumption from conventional von Neumann computer architectures. Among the emerging neuromorphic electronic devices, ferroelectric-based artificial synapses have attracted extensive interest for their good controllability, deterministic resistance switching, large output signal dynamic range, and excellent retention. This Perspective briefly reviews the recent progress of two- and three-terminal ferroelectric artificial synapses represented by ferroelectric tunnel junctions and ferroelectric field effect transistors, respectively. The structure and operational mechanism of the devices are described, and existing issues inhibiting high-performance synaptic devices and corresponding solutions are discussed, including the linearity and symmetry of synaptic weight updates, power consumption, and device miniaturization. Functions required for advanced neuromorphic systems, such as multimodal and multi-timescale synaptic plasticity, are also summarized. Finally, the remaining challenges in ferroelectric synapses and possible countermeasures are outlined.

All‐Electrical Detection of the Spin‐Charge Conversion in Nanodevices Based on SrTiO3 2‐D Electron Gases

AbstractThe Magnetoelectric Spin‐Orbit (MESO) technology aims to bring logic into memory by combining a ferromagnet with a magnetoelectric (ME) element for information writing, and a spin‐orbit (SO) element for information read‐out through spin‐charge conversion. Among candidate SO materials to achieve a large MESO output signal, oxide Rashba two‐dimensional electron gases (2DEGs) have shown very large spin‐charge conversion efficiencies, albeit mostly in spin‐pumping experiments. Here, all‐electrical spin‐injection and spin‐charge conversion experiments in nanoscale devices harnessing the inverse Edelstein effect of SrTiO3 2DEGs are reported. Nanodevices aredesigned, patterned, and fabricated in which a spin current injected from a cobalt layer into the 2DEG is converted into a charge current. The spin‐charge conversion signal is optimized by applying back‐gate voltages and studied its temperature evolution. It further disentangles the inverse Edelstein contribution from spurious effects such as the planar Hall effect, the anomalous Hall effect, or the anisotropic magnetoresistance. The combination of non‐volatility and high energy efficiency of these devices can potentially lead to new technology paradigms for beyond‐CMOS computing architectures.

Spin‐Orbit Readout Using Thin Films of Topological Insulator Sb2Te3 Deposited by Industrial Magnetron Sputtering

AbstractDriving a spin‐logic circuit requires the production of a large output signal by spin‐charge interconversion in spin‐orbit readout devices. This should be possible by using topological insulators, which are known for their high spin‐charge interconversion efficiency. However, high‐quality topological insulators have so far only been obtained on a small scale, or with large scale deposition techniques that are not compatible with conventional industrial deposition processes. The nanopatterning and electrical spin injection into these materials have also proven difficult due to their fragile structure and low spin conductance. The fabrication of a spin‐orbit readout device from the topological insulator Sb2Te3 deposited by large‐scale industrial magnetron sputtering on SiO2 is presented. Despite a modification of the Sb2Te3 layer structural properties during the device nanofabrication, a sizeable output voltage is measured that can be unambiguously ascribed to a spin‐charge interconversion process. The results pave the way for the integration of layered van der Waals materials in spin‐logic devices.

Analysis of Trapping Effect on Large-Signal Characteristics of GaN HEMTs Using X-Parameters and UV Illumination.

GaN high-electron-mobility transistors (HEMTs) have attracted widespread attention for high-power microwave applications, owing to their superior properties. However, the charge trapping effect has limitations to its performance. To study the trapping effect on the device large-signal behavior, AlGaN/GaN HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) were characterized through X-parameter measurements under ultraviolet (UV) illumination. For HEMTs without passivation, the magnitude of the large-signal output wave (X21FB) and small-signal forward gain (X2111S) at fundamental frequency increased, whereas the large-signal second harmonic output wave (X22FB) decreased when the device was exposed to UV light, resulting from the photoconductive effect and suppression of buffer-related trapping. For MIS-HEMTs with SiN passivation, much higher X21FB and X2111S have been obtained compared with HEMTs. It suggests that better RF power performance can be achieved by removing the surface state. Moreover, the X-parameters of the MIS-HEMT are less dependent on UV light, since the light-induced performance enhancement is offset by excess traps in the SiN layer excited by UV light. The radio frequency (RF) power parameters and signal waveforms were further obtained based on the X-parameter model. The variation of RF current gain and distortion with light was consistent with the measurement results of X-parameters. Therefore, the trap number in the AlGaN surface, GaN buffer, and SiN layer must be minimized for a good large-signal performance of AlGaN/GaN transistors.

Study of In x Ga1-x N/GaN Homotype Heterojunction IMPATT Diodes

In this work, a novel n-In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-<i>x</i></sub> N/N-gallium nitride (GaN) homotype heterostructure is proposed instead of P-GaN/N-GaN homostructure to produce impact-ionization-avalanche-transit-time (IMPATT) diode. Conventional GaN IMPATT device will lose its working ability due to the immature p-type GaN, so this work predicts that the n-In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-<i>x</i></sub> N/N-GaN IMPATT diode can be an alternative to the GaN p-n IMPATT diode; thus, the difficulty of the p-type doping process is avoided. The dc and RF large-signal output characteristics with different compositions are investigated in detail. The simulation results show that the power and efficiency of the novel structure device increase when the In composition increases. When the In composition is greater than 0.4, the performance of the homotype heterojunction IMPATT is better than that of p-n IMPATT. Moreover, homotype heterojunction IMPATT is better in frequency bandwidth, and it can hold greater bias current density than p-n IMPATT. Meanwhile, the performance of homotype heterojunction IMPATT does not depend on the thickness of the InGaN layer, but it decreases as the thickness of the p-type region in p-n IMPATT increases. As it has greater potential in the application, this work brings a reference for the design and manufacture of IMPATT devices based on wide bandgap semiconductor materials, especially GaN materials.

Piezoionic sensors based on formulated PEDOT:PSS and Aquivion® for ionic polymer–polymer composites

In this work, an ionic polymer–polymer composites (IP2Cs) was developed as piezoionic sensors based on Aquivion® perfluorinated conducting membranes and modified PEDOT:PSS electrodes. The influence of solvent annealing, additive concentration and its nature (ionic liquid (IL), Aquivion®,…) on the electronic conductivity and the mechanical properties of modified PEDOT:PSS electrodes is investigated. The design of flexible free-standing PEDOT:PSS electrodes provides a new way of IP2Cs conception. Tri-layers are elaborated either by drop-casting or by thermocompressing of electrodes on top of commercial Aquivion® membranes swelled by an IL 1-ethyl-3-methylimidazolium bis (trifluoromethyl-sulfonyl) imide. The open-circuit voltage output is measured during bending stimulation experiments as function of the mechanical perturbation amplitude. These IP2Cs made from Aquivion® behaves as soft mechanical strain sensors with large electrical output signal as high as ΔE = 2.9 mV (Δϵ = ±2%) under optimal conditions. The influence of the IP2C’s manufacturing process, grade of Aquivion® membrane, and electrode’s properties is investigated. This study emphasized the significant contribution of the electrode’s mechanical properties that appears as a critical parameter for the development of high performance piezoionic sensors. In the near future, we will explore the opportunity to employ these Aquivion®-based IP2Cs as soft strain sensors for robotic and medical applications.

Surface morphology features of point contact gas sensors based on Cu-TCNQ compound

The 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anion salt compound was used as the sensitive material of gas point contact sensors. The phase composition and surface morphology of the obtained sensor films were established. It was found correlation between surface morphology of the point-contact transducer and definite type of the sensor response curve observed under action of the human breath gas. If the sensor sample is formed from numerical crystals of the same or similar sizes having a uniform shape, similar to a shell, and clearly defined external borders it indicates to the creation of defect-free Yanson point contacts in the process of soft electrochemical synthesis. As a result, the surface of the sensor is a complex multistructure of a numerous number of Yanson point contacts, which generates a large output signal from the sensor in response to the action of the analyte. When crystals of Cu-TCNQ compound forming samples under investigation have lower density, large size, distorted and full of fractures boundaries, it prevents the formation of high-quality point contacts. These morphologic peculiarities are typical for samples with low level of response signal. In the case of extremely low density of Cu-TCNQ crystals observed in the sample surface the sample does not show any response to the action of the human breath gas.

A D-Band Power Amplifier in 65-nm CMOS by Adopting Simultaneous Output Power-and Gain-Matched Gmax-Core

This paper proposes a simultaneous output power- and gain-matching technique in a sub-THz power amplifier (PA) design based on a maximum achievable gain ( G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) core. The optimum combination of three-passive-elements-based embedding networks for implementing the G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> -core is chosen considering the small- and large-signal performances at the same time. By adopting the proposed technique, the simultaneous output power- and gain-matching can be achieved, maximizing the small-signal power gain and large-signal output power simultaneously. A 150 GHz single-ended two-stage PA without power combining circuit is implemented in a 65-nm CMOS process based on the proposed technique. The amplifier achieves a peak power gain of 17.5 dB, peak power added efficiency (PAE) of 13.3 and 16.1 %, saturated output power ( P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> ) of 10.3 and 9.4 dBm, and DC power consumption of 86.3 and 52.4 mW, respectively, under the bias voltage of 1.2 and 1 V, which corresponds to the highest PAE, gain per stage and P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> per single transistor among other reported CMOS D-band PAs.

AlInGaN/GaN HEMTs With High Johnson’s Figure-of-Merit on Low Resistivity Silicon Substrate

This work demonstrates high-performance AlInGaN/AlN/GaN high electron mobility transistors grown on 150 mm p-type low resistivity (resistivity~ 20-100 Ω-cm) silicon substrate with state-of-the-art Johnson's figure-of-merit (JFOM). Current gain cut-off frequency (fT) of 83 GHz and 63 GHz and power gain cut-off frequency (fmax) of 95 GHz and 77 GHz with a three-terminal off-state breakdown voltage of 69 V and 127 V, resulting in a high JFOM of 5.7 THz-V and 8.1 THz-V are achieved on the devices with a gate length of 0.16 μm and gate to drain distance of 2 μm and 4 μm, respectively. The fT and J-FOM are comparable or better than the reported values obtained on high resistivity silicon and SiC substrates for devices with similar gate length. On the other hand, GaN-on-Si HEMT structure on the LR-Si substrate exhibits lower power gain and power added efficiency due to strong capacitive coupling effects. TCAD large signal output power simulation indicates significant improvements in output power by minimizing the defects and free charge carriers in the GaN buffer even in the presence of the parasitic channel conduction and conductive silicon substrate. We further propose a modified equivalent circuit model of the parasitic conduction to take into account the conductivity of the GaN and AlGaN buffer.

Performance of hydrogenated diamond field-effect transistors on single and polycrystalline diamond

In this work, we investigate the influence of defect concentration of the diamond substrates on the performance of hydrogen-terminated diamond field-effect transistors by Raman spectra, pulsed I–V characteristics analysis, and radio frequency performances measurements. It is found that a sample with higher defect concentration shows larger drain-lag effect and lower large-signal output power density. Defects in the diamond act as traps in the carrier transport and have a considerable influence on the large-signal output power density of diamond field-effect transistors. This work should be helpful for further performance improvement of the microwave power diamond devices.

Analysis of Large-Signal Output Capacitance of Transistors Using Sawyer–Tower Circuit

A detailed analysis of the Sawyer–Tower method used in the measurement of large-signal output capacitance ( $\boldsymbol {C}_{{\textrm {o}}}$ ) of power transistors is presented, followed by important design recommendations to obtain accurate results. Key factors affecting the proper implementation of the technique, such as power amplifier characteristics, load slew rate, reference capacitor ( $\boldsymbol {C}_{\text {ref}}$ ), and reverse conduction of the device, are addressed, with accompanying simulation and experimental results for Si, SiC, and GaN devices. A thorough investigation of the selection of $\boldsymbol {C}_{\text {ref}}$ is presented, with a new equation to correctly determine its value for a given voltage swing and output capacitance range of the device under test (DUT). We report that the Sawyer–Tower circuit imposes the DUT to enter steady-state reverse conduction under certain conditions, thus leading to charge–voltage ( QV ) hysteresis patterns unrelated to $\boldsymbol {C}_{{\textrm {o}}}$ . Our analysis reveals that the origin of this phenomenon is related to DUT’s leakage current and it could be minimized by the proper selection of excitation frequency. This article intends to provide an effective guide on designing and using the Sawyer–Tower circuit, and to induce further scientific insight on characterizing $\boldsymbol {C}_{{\textrm {o}}}$ .

Evaluation of parasitic resistance in voltage-driven electrical resistance tomography

Electrical resistance tomography (ERT) is an effective method for monitoring electrical conductivity distribution in the field using boundary measurement information. In applications with a large pipe diameter and large load variation, voltage-driven ERT (ERTv) can overcome the limitations of current-driven ERT (ERTc). A voltage source is used in ERTv to apply an excitation signal to the electrode, and can provide a large output signal. Meanwhile, saturation will not occur when the load of the field shows large fluctuations. However, the main disadvantage of an ERTv system is that the parasitic resistance in the system has an influence on the measurement results which cannot be ignored. The existence of parasitic resistance can cause measurement errors and reduce the reliability of ERTv systems. In this paper, the influence of parasitic resistance was evaluated and the trend of variation of this effect with different background conductivities was studied. The index kr was defined to find the relationship between parasitic resistance and background conductivity. When , the reconstructed image can better reflect the actual conductivity distribution. At the same time, the applicable background conductivity range of the system can be acquired according to kr, when the value of parasitic resistance in the system is known in advance.

Dual-Band Balanced-to-Unbalanced Power Divider With Independent Power Division Ratios

A dual-band balanced to unbalanced power divider with independent power division ratios (PDRs) at two operating frequencies is proposed in this article. The proposed power divider includes a dual-band phase inverter, a grounded resistor, and four transmission-line sections (TLS). By simultaneously changing characteristic impedances and electrical lengths of the four TLS, the independent PDRs are obtained, and the large-signal output port at lower and upper operation bands can be different. Compared to the previous works, it has more flexibility in the power division. Moreover, the closed-form design equations are provided and discussed. To verify the proposed structure, two BTU power dividers operating at 1.0 and 2.0 GHz are designed, fabricated, and measured. The PDRs of the first power divider are -6 and 6 dB for the lower and upper operation bands, respectively. The second power divider has the PDRs of 3 and -6 dB. The measured results are good agreements with the theoretical calculation and electromagnetic simulation.

Measurement of Large-Signal C OSS and C OSS Losses of Transistors Based on Nonlinear Resonance

In this letter, we present a new measurement technique to evaluate the large-signal output capacitance ( C OSS) of transistors as well as the C OSS energy dissipation ( E DISS), based on the nonlinear resonance between a known inductor and the output capacitance of the device under test. The method is simple and robust, and only requires a single voltage measurement to extract the large-signal C OSS both in charging and discharging transients. By changing the circuit parameters, it is possible to tune the resonance frequency (even above 40 MHz) and the voltage swing (even above 1 kV) with d v /d t exceeding 100 V/ns, even though the method relies only on a low-voltage dc source, without the need for high-voltage RF amplifiers. The single-pulse operation of the method enables measuring C OSS and E DISS at very high frequency and d v /d t values without any thermal runaway. Using the proposed method, we extracted large-signal C OSS and E DISS of power transistors based on different semiconductor technologies. The obtained results were verified by Sawyer–Tower method and data reported in the literature. In particular, dv/dt-independent C OSS losses were measured in cascode GaN transistors. The precise characterization of large-signal C OSS of transistors presented in this letter is essential for the design of power converters, especially those operating at high switching frequencies.

Deprotonation-Induced Conductivity Shift of Polyethylenedioxythiophenes in Aqueous Solutions: The Effects of Side-Chain Length and Polymer Composition.

Deprotonation-induced conductivity shift of poly(3,4-ethylenedixoythiophene)s (PEDOTs) in aqueous solutions is a promising platform for chemical or biological sensor due to its large signal output and minimum effect from material morphology. Carboxylic acid group functionalized poly(Cn-EDOT-COOH)s are synthesized and electrodeposited on microelectrodes. The microelectrodes are utilized to study the effect of carboxylic acid side-chain length on the conductivity curve profiles in aqueous buffer with different pH. The conductivity shifts due to the buffer pH are effected by the length of the carboxylic acid side-chains. The shifts can be explained by the carboxylic acid dissociation property (pKa) at the solid–liquid interface, self-doping effect, and effective conjugation length. Conductivity profiles of poly(EDOT-OH-co-C2-EDOT-COOH) copolymers are also studied. The shifts show linear relationship with the feed monomer composition used in electrochemical polymerization.

A Self-Powered Vibration Sensor With Wide Bandwidth

A self-powered vibration sensor based on electromagnetic induction is presented in this paper. The vibration sensor is implemented with stacked flexible coils and polymeric springs. The stacked flexible coil enables large output signal, while long and flexible springs enable high sensitivity and wide linear range of the sensor. At resonance, the sensor has a sensitivity of 1.83 V/g and a maximum resolution of 0.002 g. In the high-frequency range, where the sensor output is frequency-independent (100–3000 Hz), the sensor has a sensitivity of 66.5 mV/g, a maximum resolution of 0.05 g, and a measurement range up to 8.5 g.

An X-Band 40 W Power Amplifier GaN MMIC Design by Using Equivalent Output Impedance Model

This paper presents an X-band 40 W power amplifier with high efficiency based on 0.25 μm GaN HEMT (High Electron Mobility Transistor) on SiC process. An equivalent RC (Resistance Capacitance) model is presented to provide accurate large-signal output impedances of GaN HEMTs with arbitrary dimensions. By introducing the band-pass filter topology, broadband impedance matching networks are achieved based on the RC model, and the power amplifier MMIC (Monolithic Microwave Integrated Circuit) with enhanced bandwidth is realized. The measurement results show that this power amplifier at 28 V operation voltage achieved over 40 W output power, 44.7% power-added efficiency and 22 dB power gain from 8 GHz to 12 GHz. The total chip size is 3.20 mm × 3.45 mm.